Electrical testing apparatus



May 16, 1950 s. E, FRISBIE ETAT. 2,507,565

ELECTRICAL TESTING APPARATUS Filed Aug. C50, 1948 Patented May i6, 1350 ELECTRICAL TESTING APPARATUS Stewart E. Frisbe, Danville, and Gilbert E. Weelis,

Chicago, Ill., assignors, by direct and mesne assignments, to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application August 30, 1948, Serial No. 46,793

4 Claims. l

This invention relates to electrical testing apparatus and more particularly to automatic con denser testing apparatus.

An object of this invention is to provide a new and eilcient apparatus for determining electrical characteristics of articles.

In accordance with one embodiment of this invention an apparatus for ascertaining whether or not the capacity of a condenser falls between predetermined maximum and minimum limits is provided with a microfarad meter which is responsive to the capacity of a condenser under test and which is adapted to close a circuit to a relay if the capacity oi the condenser is above the minimum and also to close a circuit to a second relay if the capacity is below the permitted maximum capacity. The two relays, when operated contemporaneously, close a circuit to an acceptance device for either indicating a successful test or for mechanically providing the acceptance of a condenser which successfully passes the test.

A complete understanding or" the invention will be had by referring to the following detailed description taken in conjunction with the accompanying single figure drawing which diagrammatically illustrates the invention.

The apparatus described herein may be used to eheclr the capacity of a single condenser 3 or two condensers t and simultaneously, the condenser or condensers under test being placed in a test xture 5 which supports the condensers and connects them with the test circuit. The object of the test is to energize the operating coil 6 of an acceptance device i ii the capacity of the condenser under test falls within the required maximum and minimum limits. In case the condenser under test should fail the test, then the operating coil 6 is to remain deenergized. The acceptance device l may be an indicator or it may be a mechanical device for causing the separating oi goed condensers from bad ones. When energized the operating coil 6 receives its electrical power from a source of electrical current 8 through a closed switch 9 and the closed contacts I0 and Il of relays l2 and I3, respectively, the relay I2 being energized if the capacitance under test is below the maximum limit and the relay I3 being energized if the capacitance under test is above the minimum limit. The relays I2 and I3 are operable in response to the capacity registered on a pair of capacitance measuring devices Il and I5 known' as microfarad meters. The two meters being similar in construction, only the one designated I 4 will be described in detail.

The meter Il is provided with an impedance network including condensers i6 and il', a moving coil assembly I8 for carrying an indicating needle 20, a eld coil 2l and a resistor 22. To operate the meter a iixed frequency alternating current 5 from the source 3 is applied to the impedance network through meter terminals 2li and 2E when a switch 26 is closed. Capacitances to be measured are connected to the terminal t@ and a terminal 30 thus effecting a change in the irn- 10 pedance of the networlr and causing the moving coil assembly i8 to move relative to the field coil 2l thereby moving the needle iii across a scale 3l which, in a normal microiarad meter, is calibrated in units of capacity.

The meter ld is provided with means operable in response to the capacity of the condenser under test for closing external circuits to operate the relays l2 and i3. Two meta ic contact segments 32 and 33 are mounted 's 'to each other in predetermined cut-aout portiers ci the meter scale representing conditions above and below a predetermined capacity. The two segments are insulated from each other and the physical da tance between them is as small as pcssible without the two segments touching. at its upper end; the needle 20 is provided with a contact 3d which is adapted, when the end of the needle depressed, to engage either contact 32 or 33 depending on its position along the meter scale. in order to den 2o pre-ss the end of the needle 23 when desired, a relay 38 operable from a source or electrical power 39 through a switch 40 is mounted on the meter I4 and is provided with a movable armature 4I which, upon the energization oi the relay 3.3 38, will operate a metallic depressor bar d2 to force the contact 3d to engage either ci the segments 32'or 33. When depressed the contact 3d engages not only the segment below it but also the metallic depressor bar t2 thereby forms 4o ing lan electrical connection between the depresm sor bar and either of the contact segments or 33. The depressor bar 42 is connected to one side 43 of the source of power 39 whose other side M is grounded. Contact segment 32 is connected to ,115 one end of the operating coil 53 of the relay I2, and contact segment 33 is connected to one end of the operating coil 5I of the relay i3. The other ends of the operating-coils and 5I may, by

means of a switch 52, be connected directly to ground or to contact segments 53 and 54, respectively, of the microfarad meter I5 whose depressor bar 60 is connected to ground. A relay 10 for operating the depressor bar 60 is connected in parallel with the relay 38 to operate simul- 55 taneously therewith.

normally open contacts I0, 6I and 62 which close when the operating coil l of the relay is energized, and the relay I3 is provided with three sets s of normally open contacts I I, 63 and 84 which close when the relay coil 5I is energized, both coils 50 and 5I obtaining operating current from the source 39 when the proper circuits are closed.

During the operation oi the apparatus it is required that the space on the scale between the contact segments 32 and 33 represent the minimum permittedcapacity at one time and the maximum permitted capacity at another time. In order to eiect these conditions and to extend the range 'of condensers that may be tested with microfarad meters having a particular range, standard condensers 1I, 12, I3 and 'Il having variable capacitance ranges are connectable in series or in parallel with the condenser unit under test, depending on whether the condenser under test is above or below the range of the meter used, thereby producing a resultant capacitance within the range of the meter used.

Two standard condensers are used in the test for each condenser unit. One standard condenser is adjusted to a predetermined capacitance to be used in the test for minimum permissible capacity and the other standard condenser is adjusted to a capacitance value to be used in the test for maximum permissible capacity. This is accomplished in the following manner: In the case of condensers under test that have permissible limits below the range of the microfarad meter, sufcient capacitance in one of the standard condensers is connected in parallel with the condenser under test to make the resultant sum of the capacitance of the standard condenser and the maximum permissible capacitance of the condenser under test equal to the capacitance value representing the division point between the two contact segments on the meter scale. In a like manner capacitance from a second standard condenser is paralleled with the condenser under test to make the resultant sum of the standard condenser capacitance and the minimum permissible capacitance of the condenser under test equal to the capacitance value representing the division point between the two contact points on the meter scale. For example, if the capacitance value representing the division point between the contact segments on the meter scale is .63 microfarad and the condenser to be tested has the permissible limits of maximum .13 microfarad and minimum .10 microfarad, then the standard condenser used in maximum limit test should have a value of .50 microfarad and the standard condenser used in the minimum limit test should have a value of .53 microfarad.

In case of condensers under test that have permissible limits above the range of the microfarad meter suillcient capacitance from one of the standard condensers is connected in series with the condenser under test to make the resultant capacitance of the standard condenser and the maximum permissible capacitance of the condenser under test equal to the capacitance value representing the division point between the contact segments on the meter. Similarly sufdcient capacitance from the second standard condenser box is connected in series with the condenser under test to .make the resultant capacitance of the standard condenser and the minimum permissible capacitance of the condenser under test equal to the capacitance value representing the division point between the two contact segments Aon the scale of the mircoiarad meter. For example. if the capacitance representing the division point between the contact segments on the meter is .63 microfarad and the condenser to be tested has the permissible limits of maximum 2.50 and minimum 2.00 microfarads, then the standard condenser used in the minimum .linut test should have a capacitance value of .92 microfarad and the capacitance value of the standard condenser'to be used in the maximum limit test yshould be .84 microfarad.

Standard condensers 'II and 'I2 are the standards associated with the condenser 3 under test and the microfarad meter I4, and the standard condensers 'I3 and 'Il are the standards associated with the condenser l under test and the microfarad meter I5. Switches 80 and 8| provide a means for selecting the minimum and maximum Standard for the respective condensers under test, and switches 82 and 83 are used to connect the selected standard condensers either in series or in parallel with the associated condenser unit under test. For example, when the switches 82 and 83 are in their upward position the selected standard condensers will be in series with the condensers under test, and if these switches are operated downward, then the selected standard condensers will be in parallel with the condensers under test.

A single condenser unit 3 may be checked for maximum and minimum capacitance by connecting the unit to the test xture 5, as indicated in the drawing, which also illustrates the initial positions of all the switches for this test. Since a single unit is being tested, condenser 4 will not be connected to the test fixture. The position of switch 82 will depend on whether the range of the microfarad meter I 4 is above or below the required capacity of the condenser 3. With switch 30 in the downward position shown in the drawing the standard condenser l2 is connected in series with condenser 3 and the meter M. As- 1 suming that condencer 'I2 is the maximum standard then the space between the contact segments 32 and 33 of the meter I4 will represent the maximum permissible limit of capacitance.

To power the meter I d switch 26 is closed, and if the capacitance of the condenser 3 is less than the maximum, then the needle 20 of the meter I4 will swing to the right from its zero position at the left and will come to rest at some point to the left of the space between the contact segments 32 and 33 and above the segment 32. Switch is then closed for a short time to energize the relay 38 and operate the depressor bar 42. This depresses the needle 20 to complete an electrical path between the depressor bar and the contact 32 and closes the circuit from the source 39 to the operating coil50 of the relay I2 thereby operating the relay to close the contacts I 0, 6I and $2. Since closure of the contacts Si furnishes current from the source 39 to the coil 50 by an alternative path, the switch may be opened to release relay 38, and the relay I2 will remain locked after contact is broken between the depressor bar 42 and the contact segment 32.

Next the switch is operated upward to connect the minimum standard condenser 1I into the circuit with condenser 3 and the meter I4, thereby making the space between the contact segments 32 and 33 representative of the minimum permissible capacitance. If the capacitance of the condenser 3 is higher than the minimum limit,

then the needle 20 will swing to the right and 8 between the contact segments l2 and 33 and above to ground. Switch I0 is then opened and switches the segment 33. Switch 40 is then closed to de- 80 and 8l are operatedupward to connect the and the switch 40 may be opened. to rest in a position to the right of the critical Both relays l2 and I3 being locked in en 0P- points on the meters and above the contact segerated position, an electrical path is completed ments 33 and 54 of the respective meters, and from the open switch 9 to the operating coil m upon operation of the depressor bars 42 and il switch of the acceptance device 'I through closed by the closure of switch 4D, the operating coil contacts i0 and il. It will be noted that the 5I of the relay i3 will be energized to operate other end of the coil 6 is connected to one side the relay and close contacts Ii, 63 and 6e. The of the source oi electrical current 8 and that current path from the source 39 to the coil 5l is the other side of the source 8 is connected to |5 as follows: From the terminal source 43 through the switch 9. To complete the test the switch the depressor bar 42, .the needle contact 3l, the t is operated, thus energizing the coil 6 withv Contact segment 33, the coil 5i, the switch 52, electrical current from the source 8. As pointed the contact segment 56, the needle contact 90, out before, the fact that the coil 6 has been the depressor har $0 and thence through ground energized at the end of the test indicates that 20 to the terminal 46 oi the source 39. Relays l2 the condenser unit 3 under test passed the test and i3 are locked, and when switch 9 is closed, successfully in that its capacitance fell between the coil 6 will be energized as hereinbefore exthe maximum and minimum permissible limits. plained.

the condenser 3 had failed in either the ma'xi- Il either or tooth of the condensers 3 and I mum or minimum tests, then one of the relays 2 had failed in either or both 'the maximum and i2 or le would not have been operated and the the minimum tests, then either or hoth of the circuit between the source t' and the coil G could relays il and i3 would not have operated thereby not he completed by the closure of switch 9 and making it impossible to energize -the operating the coil would remain unenergized at the end 'coil e upon the closing of the switch 9. of the test, thus indicating that the condenser 3 si 0d that sh@ ab0ve-desgribe has failed the test. To prepare the apparatus arrangements are simply illustrative of the apror testing another condenser the switches 9 plication of the principles of the invention. Nu-

and 25 are opened, and a switch 84 is momenmerous other arrangements may "ce readily detarily opened to release the locked relays I2 vised by those skilled in the art hich will emand itl. 1"- ioody the principles of the invention and fall cases where two separate condensers 3 and within the spirit and-scope thereof.

d are mounted in a single can it may be desirable What is claimed is:

to check the capacitance conditions with respect 1. An apparatus for determining the capacito maximum and minimum limits of both contance oi condensers comprising a rst capacity densers simultaneously. To effect this, conil y densers 3 and il are connected to the test fixture be measured, said meter having a first circuit 5, as shown in the drawing. Switches 82 and 83 closing means operative in a range of values of .is as shown in the drawing with the exception spond to values of said capacitance below and of switch 52 which, for this test, Should be 0D- 50 above. respectively, of a second critical value, a era'ted t0 the right t0 00111D6015 the 10We1 ends second capacity meter responsive to an electrical 0f Operating COIS 50 and 5! t0 COHHC Segments capacitance to be determined, said second meter 53 and respectively 0f the meter |5- Switch having a rst circuit closing means operative in a 26 is then closed to power the meters I 4 and 15- range of values of said capacitance below a criti- It will be apparent that While the Captance Il cal value, said second meter also having a second of the condenser 3 will be registered on the circuit closing means operative in a range of microfarad meter i 4 the capacitance of the convalues of said Capacitance above the msg mendenser 4 Will be registered 0n the HICFOfaTad tioned critical value, variable condensers for meter I5, bOth responses being SimultaneOUS- changing the range of the second meter so that If the CaDaCitnCe 0f lOOI COHGUSGTS S below the first and second circuit closing means of said their permissible maximum 111111155 then the 1n' second meter will respond to values of sa1d capacithe respective meters' and upon Operation 0f the .l rst circuit closing means of both meters and a depreSSOr bars 42 and 50 UDOn the Closure 0f source of current and operable in response to the switch 40, the operating coil 5U of the relay I2 i contemporaneous Operation of th will be energized to operate the relay and close closing means of both meters, a Second relay COHaQS lo, 5| and 52- Current 1S received by having its operatingcoil in series with the second the 00 11 50 from the Source 39 by mans 0f the 70 circuit closing means of both meters and a source ponse to the con- SOUYCe 39 through the depresso? bal 42 the temporaneous operation of the second circuit eOi1l50. t511e Switch 52, the contact Segment 53. netic acceptance device energizable to a. nonthe needle contact 90, and the depressor bar 60 1 

